Feature request: configurable download mirror / offline model install (China network — image models stall)

[Hina52015]

Summary

Downloading the on-device image generation models (Bonsai Image 4B, FLUX.2 klein,
Z-Image Turbo) is effectively unusable for users in mainland China: the download runs
from huggingface.co / GitHub, which is heavily throttled here. Even with a VPN active
the transfer stalls (e.g. a single .gallerytmp stuck at ~110 KB). It would help a lot
to let users either point Box at a mirror, or install model files manually/offline.

Environment

• Device: Redmi K80 (Snapdragon 8 Gen 3), 12/16 GB RAM
• Android: 15
• Box version: v3.4.5 (from GitHub releases)
• Model: Bonsai Image 4B (~4.3 GB)
• Network: mainland China; VPN on; download still stalls

Steps to reproduce

1. Open Box → Image Gen → Bonsai Image 4B → Download.
2. Watch the progress.
3. Transfer stalls almost immediately.

Actual behaviour

• Exactly one temp file is created, e.g.
  Android/data/com.box.gallery/files/Bonsai_Image_4B/main/dit_gpu_int4b32.tflite.gallerytmp
• Its size stays at ~110 KB; the download never progresses.
• Setting Range/resume works in code, but the source is too slow to make progress.

Expected behaviour

• Download completes in reasonable time, OR
• A way to obtain the model without the built-in downloader.

Proposal (any of these would help)

1. Configurable download base URL / mirror. The image models are hosted at
   huggingface.co/litert-community/... and there is a well-known, much faster mirror at
   hf-mirror.com. A setting to replace the download host (or an "HF_ENDPOINT" style
   option) would fix this for everyone in CN.
2. Offline / manual install path. Allow the user to drop the official files into the
   model folder (e.g. .../files/<Model>/<version>/) and have Box recognise them, instead
   of requiring the in-app download to reach SUCCEEDED. The files are public at
   litert-community/Bonsai-Image-ternary-4B, litert-community/FLUX.2-klein-4B-LiteRT
   and litert-community/Z-Image-Turbo-LiteRT.
3. Optionally, resume-friendly mirror fallback: if the primary host stalls, retry via
   the mirror automatically.

Why this matters

Box is one of the very few apps that can run these LiteRT image models on-device, but for
a large user base the model download is the one hard blocker. Fixing the download path
would unlock the whole image-generation feature for CN users.

Thanks for the great project!